allow one zero length dash

src/utils/SkDashPathPriv.h

Index: src/utils/SkDashPathPriv.h
diff --git a/src/utils/SkDashPathPriv.h b/src/utils/SkDashPathPriv.h
index 7453dcec82e35829b80db097d005746d0996782b..54bf9a487098c118f2e0cdcdd08cb9594d7bc931 100644
--- a/src/utils/SkDashPathPriv.h
+++ b/src/utils/SkDashPathPriv.h
@@ -16,17 +16,25 @@ namespace SkDashPath {
      * inputed phase and intervals. If adjustedPhase is passed in, then the phase will be
      * adjusted to be between 0 and intervalLength. The result will be stored in adjustedPhase.
      * If adjustedPhase is nullptr then it is assumed phase is already between 0 and intervalLength
+     *
+     * Caller should have already used ValidDashPath to exclude invalid data.
      */
     void CalcDashParameters(SkScalar phase, const SkScalar intervals[], int32_t count,
                             SkScalar* initialDashLength, int32_t* initialDashIndex,
                             SkScalar* intervalLength, SkScalar* adjustedPhase = nullptr);
 
     bool FilterDashPath(SkPath* dst, const SkPath& src, SkStrokeRec*, const SkRect*,
-                        const SkScalar aIntervals[], int32_t count, SkScalar initialDashLength,
-                        int32_t initialDashIndex, SkScalar intervalLength);
-    
-    bool FilterDashPath(SkPath* dst, const SkPath& src, SkStrokeRec*, const SkRect*,
                         const SkPathEffect::DashInfo& info);
+
+    /*
+     * Caller should have already used ValidDashPath to exclude invalid data.
+     */
+    bool InternalFilter(SkPath* dst, const SkPath& src, SkStrokeRec* rec,
+                        const SkRect* cullRect, const SkScalar aIntervals[],
+                        int32_t count, SkScalar initialDashLength, int32_t initialDashIndex,
+                        SkScalar intervalLength);
+
+    bool ValidDashPath(SkScalar phase, const SkScalar intervals[], int32_t count);
 }
 
 #endif